drm/imx/dcss: include drm/drm_bridge.h header

Compile-testing random configurations leads to failures in
dcss-kms.c from a missing declaration:

drivers/gpu/drm/imx/dcss/dcss-kms.c:95:8: error: use of undeclared identifier 'drm_bridge_attach'
   95 |         ret = drm_bridge_attach(encoder, bridge, NULL,
      |               ^
drivers/gpu/drm/imx/dcss/dcss-kms.c:96:5: error: use of undeclared identifier 'DRM_BRIDGE_ATTACH_NO_CONNECTOR'
   96 |                                 DRM_BRIDGE_ATTACH_NO_CONNECTOR);
      |                                 ^

Include the header directly.

Fixes: 004555a1 ("drm/imx/dcss: Allow build with COMPILE_TEST=y")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Dave Airlie <airlied@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20241028163527.2425783-1-arnd@kernel.org